Systems and methods for making and using a lead introducer for an implantable electrical stimulation system

ABSTRACT

A lead introducer includes an outer needle with a sharpened distal tip and an open channel extending along an entire length of the outer needle. An inner needle slides along the open channel of the outer needle. The inner needle includes a blunt distal tip. A biasing element is coupled to the inner needle and facilitates transition of the inner-needle distal tip between a distally-biased position, where the inner-needle distal tip obstructs the sharpened outer-needle distal tip, and a retracted position, where the inner-needle distal tip exposes the sharpened outer-needle distal tip. A splittable member is disposable over the outer needle when the inner needle is disposed in the open channel of the outer needle. The splittable member is separatable from the inner and outer needles along at least one perforated region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Ser. No. 61/874,718, filed Sep. 6, 2013,which is incorporated herein by reference.

FIELD

The present invention is directed to the area of implantable electricalstimulation systems and methods of making and using the systems. Thepresent invention is also directed to a lead introducer for facilitatinginsertion of implantable electrical stimulation leads havingnon-isodiametric lead bodies into patients, as well as methods of makingand using the lead introducers and electrical stimulation leads.

BACKGROUND

Implantable electrical stimulation systems have proven therapeutic in avariety of diseases and disorders. For example, spinal cord stimulationsystems have been used as a therapeutic modality for the treatment ofchronic pain syndromes. Peripheral nerve stimulation has been used totreat chronic pain syndrome and incontinence, with a number of otherapplications under investigation. Functional electrical stimulationsystems have been applied to restore some functionality to paralyzedextremities in spinal cord injury patients.

Stimulators have been developed to provide therapy for a variety oftreatments. A stimulator can include a control module (with a pulsegenerator), one or more leads, and an array of stimulator electrodes oneach lead. The stimulator electrodes are in contact with or near thenerves, muscles, or other tissue to be stimulated. The pulse generatorin the control module generates electrical pulses that are delivered bythe electrodes to body tissue.

BRIEF SUMMARY

In one embodiment, a lead introducer includes an outer needle having anouter-needle body with a proximal end portion, a distal end portion, anda longitudinal length. A sharpened distal tip is disposed along thedistal end portion of the outer-needle body. An open channel extendsalong the entire longitudinal length of the outer-needle body. An innerneedle is configured and arranged for sliding along the open channel ofthe outer needle. The inner needle includes an inner-needle body havinga proximal end portion, a distal end portion, and a longitudinal length.A blunt distal tip is disposed along the distal end portion of theinner-needle body. An inner-needle proximal hub is attached to theproximal end portion of the inner-needle body. A biasing element iscoupled to the inner-needle body. A biasing element is coupled to theinner needle and facilitates transition of the inner-needle distal tipbetween a distally-biased position, where the inner-needle distal tipobstructs the sharpened outer-needle distal tip, and a retractedposition, where the inner-needle distal tip exposes the sharpenedouter-needle distal tip. A splittable member has at least one perforatedregion extending along a longitudinal length of the splittable member.The splittable member is configured and arranged for disposing over theouter-needle body and the inner-needle body when the inner-needle bodyis disposed in the open channel of the outer-needle body and forseparating from the outer-needle body and the inner-needle body byseparating along the at least one perforated region.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic view of one embodiment of an electricalstimulation system, according to the invention;

FIG. 2A is a schematic view of one embodiment of a proximal portion of alead and a control module of an electrical stimulation system, accordingto the invention;

FIG. 2B is a schematic view of one embodiment of a proximal portion of alead and a lead extension of an electrical stimulation system, accordingto the invention;

FIG. 3 is a schematic perspective exploded view of one embodiment of alead introducer configured and arranged for facilitating implantation ofa lead of an electrical stimulation system into a patient, the leadintroducer including a multi-piece insertion needle and a splittablemember, according to the invention;

FIG. 4A is a schematic perspective view of one embodiment of the leadintroducer of FIG. 3 with the multi-piece insertion needle of the leadintroducer nested in the splittable member of the lead introducer, themulti-piece insertion needle including an inner needle in a relaxedposition such that a distal tip of the inner needle extends distallybeyond an outer needle of the multi-piece insertion needle, according tothe invention;

FIG. 4B is a schematic perspective view of one embodiment of the leadintroducer of FIG. 4A with the multi-piece insertion needle of the leadintroducer nested in the splittable member of the lead introducer, themulti-piece insertion needle including an inner needle in a retractedposition such that a distal tip of the inner needle is retracted into adistal tip of an outer needle of the multi-piece insertion needle,according to the invention;

FIG. 5A is a schematic perspective view of one embodiment of a distalend portion of the lead introducer of FIG. 4A with an inner needle ofthe lead introducer in a relaxed position such that a distal tip of theinner needle extends distally beyond an outer needle of the leadintroducer, according to the invention;

FIG. 5B is a schematic longitudinal cross-sectional view of oneembodiment of a distal end portion of the lead introducer of FIG. 5A,the lead introducer including an inner needle with a lumen opening inproximity to a distal tip of the inner needle, according to theinvention;

FIG. 6 is a schematic perspective view of one embodiment of a proximalend portion of the lead introducer of FIG. 4A with a transparent outershell, according to the invention;

FIG. 7A is a schematic longitudinal side view of one embodiment of theproximal end portion of the lead introducer of FIG. 6, the leadintroducer including a spring disposed in a proximal hub of an innerneedle, the spring disposed in a relaxed position prior to insertion ofthe lead introducer into a patient, according to the invention;

FIG. 7B is a schematic longitudinal side view of one embodiment of theproximal end portion of the lead introducer of FIG. 7A, the leadintroducer including a spring disposed in a proximal hub of an innerneedle, the spring disposed in retracted position during an initialinsertion of the lead introducer into a patient, according to theinvention;

FIG. 7C is a schematic longitudinal side view of one embodiment of theproximal end portion of the lead introducer of FIG. 6, the leadintroducer including a spring disposed in a proximal hub of an innerneedle, the spring disposed in a relaxed position subsequent to aninitial insertion of the lead introducer into a patient, according tothe invention;

FIG. 8 is a schematic perspective view of one embodiment of a distal endportion of a lead and a portion of an outer needle of the leadintroducer of FIG. 3A, the outer needle defining an open channelextending along a length of the outer needle, the open channel suitablefor receiving the lead, according to the invention;

FIG. 9 is a schematic perspective view of one embodiment of the leadintroducer of FIG. 4 partially inserted into a patient, according to theinvention;

FIG. 10 is a schematic perspective view of one embodiment of a Luer lockcollar and an inner needle removed from the lead introducer of FIG. 9and the lead of FIG. 9 aligned for insertion into an outer needle of thelead introducer, according to the invention;

FIG. 11 is a schematic perspective view of one embodiment of the outerneedle removed from the lead introducer of FIG. 10 and a splittablemember of the lead introducer of FIG. 10 being split apart to remove thesplittable member from the lead of FIG. 10, according to the invention;and

FIG. 12 is a schematic overview of one embodiment of components of astimulation system, including an electronic subassembly disposed withina control module, according to the invention.

DETAILED DESCRIPTION

The present invention is directed to the area of implantable electricalstimulation systems and methods of making and using the systems. Thepresent invention is also directed to a lead introducer for facilitatinginsertion of implantable electrical stimulation leads havingnon-isodiametric lead bodies into patients, as well as methods of makingand using the lead introducers and electrical stimulation leads.

Suitable implantable electrical stimulation systems include, but are notlimited to, a least one lead with one or more electrodes disposed alonga distal end of the lead and one or more terminals disposed along theone or more proximal ends of the lead. Leads include, for example,percutaneous leads, paddle leads, and cuff leads. Examples of electricalstimulation systems with leads are found in, for example, U.S. Pat. Nos.6,181,969; 6,516,227; 6,609,029; 6,609,032; 6,741,892; 7,949,395;7,244,150; 7,672,734; 7,761,165; 7,974,706; 8,175,710; 8,224,450; and8,364,278; and U.S. Patent Application Publication No. 2007/0150036, allof which are incorporated by reference.

FIG. 1 illustrates schematically one embodiment of an electricalstimulation system 100. The electrical stimulation system includes acontrol module (e.g., a stimulator or pulse generator) 102 and a lead103 coupleable to the control module 102. The lead 103 includes one ormore lead bodies 106, an array of electrodes 133, such as electrode 134and an array of terminals (e.g., 210 in FIG. 2A-2B) disposed along theone or more lead bodies 106. In at least some embodiments, the lead isisodiametric along a longitudinal length of the lead body 106. In FIG.1, the electrical stimulation system 100 is shown having a junction 108configured to couple to distal portion of the lead 103 to one or moreproximal portions 109 a and 109 b.

The lead 103 can be coupled to the control module 102 in any suitablemanner. In at least some embodiments, the lead 103 couples directly tothe control module 102. In at least some other embodiments, the lead 103couples to the control module 102 via one or more intermediate devices(200 in FIGS. 2A-2B). For example, in at least some embodiments one ormore lead extensions 224 (see e.g., FIG. 2B) can be disposed between thelead 103 and the control module 102 to extend the distance between thelead 103 and the control module 102. Other intermediate devices may beused in addition to, or in lieu of, one or more lead extensionsincluding, for example, a splitter, an adaptor, or the like orcombinations thereof. It will be understood that, in the case where theelectrical stimulation system 100 includes multiple elongated devicesdisposed between the lead 103 and the control module 102, theintermediate devices may be configured into any suitable arrangement.

The control module 102 typically includes a connector housing 112 and asealed electronics housing 114. An electronic subassembly 110 and anoptional power source 120 are disposed in the electronics housing 114. Acontrol module connector 144 is disposed in the connector housing 112.The control module connector 144 is configured and arranged to make anelectrical connection between the lead 103 and the electronicsubassembly 110 of the control module 102.

The electrical stimulation system or components of the electricalstimulation system, including one or more of the lead bodies 106 and thecontrol module 102, are typically implanted into the body of a patient.The electrical stimulation system can be used for a variety ofapplications including, but not limited to, brain stimulation, neuralstimulation, spinal cord stimulation, muscle stimulation, and the like.

The electrodes 134 can be formed using any conductive, biocompatiblematerial. Examples of suitable materials include metals, alloys,conductive polymers, conductive carbon, and the like, as well ascombinations thereof. In at least some embodiments, one or more of theelectrodes 134 are formed from one or more of: platinum, platinumiridium, palladium, palladium rhodium, or titanium. The number ofelectrodes 134 in each array 133 may vary. For example, there can betwo, four, six, eight, ten, twelve, fourteen, sixteen, or moreelectrodes 134. As will be recognized, other numbers of electrodes 134may also be used.

The electrodes of the one or more lead bodies 106 are typically disposedin, or separated by, a non-conductive, biocompatible material such as,for example, silicone, polyurethane, polyetheretherketone (“PEEK”),epoxy, and the like or combinations thereof. The lead bodies 106 may beformed in the desired shape by any process including, for example,molding (including injection molding), casting, and the like. Thenon-conductive material typically extends from the distal end of the oneor more lead bodies 106 to the proximal end of each of the one or morelead bodies 106.

Terminals (e.g., 210 in FIGS. 2A-2B) are typically disposed along theproximal end of the one or more proximal portions of the electricalstimulation system 100 (as well as any splitters, lead extensions,adaptors, or the like) for electrical connection to correspondingconnector contacts (e.g., 214 in FIGS. 2A-2B; and 240 in FIG. 2B). Theconnector contacts are disposed in connectors (e.g., 144 in FIGS. 1-2B;and 222 in FIG. 2B) which, in turn, are disposed on, for example, thecontrol module 102 (or a lead extension, a splitter, an adaptor, or thelike). Electrically conductive wires, cables, or the like (not shown)extend from the terminals to the electrodes 134. Typically, one or moreelectrodes 134 are electrically coupled to each terminal. In at leastsome embodiments, each terminal is only connected to one electrode 134.

The electrically conductive wires (“conductors”) may be embedded in thenon-conductive material of the lead body 106 or can be disposed in oneor more lumens (not shown) extending along the lead body 106. In someembodiments, there is an individual lumen for each conductor. In otherembodiments, two or more conductors extend through a lumen. There mayalso be one or more lumens (not shown) that open at, or near, theproximal end of the lead body 106, for example, for inserting a styletto facilitate placement of the lead body 106 within a body of a patient.Additionally, there may be one or more lumens (not shown) that open at,or near, the distal end of the lead body 106, for example, for infusionof drugs or medication into the site of implantation of the one or morelead bodies 106. In at least one embodiment, the one or more lumens areflushed continually, or on a regular basis, with saline, epidural fluid,or the like. In at least some embodiments, the one or more lumens arepermanently or removably sealable at the distal end.

FIG. 2A is a schematic side view of one embodiment of a proximal end ofone or more elongated devices 200 configured and arranged for couplingto one embodiment of the control module connector 144. The one or moreelongated devices may include, for example, the lead body 106, one ormore intermediate devices (e.g., a splitter, the lead extension 224 ofFIG. 2B, an adaptor, or the like or combinations thereof), or acombination thereof.

The control module connector 144 defines at least one port into which aproximal end of the elongated device 200 can be inserted, as shown bydirectional arrows 212 a and 212 b. In FIG. 2A (and in other figures),the connector housing 112 is shown having two ports 204 a and 204 b. Theconnector housing 112 can define any suitable number of ports including,for example, one, two, three, four, five, six, seven, eight, or moreports.

The control module connector 144 also includes a plurality of connectorcontacts, such as connector contact 214, disposed within each port 204 aand 204 b. When the elongated device 200 is inserted into the ports 204a and 204 b, the connector contacts 214 can be aligned with a pluralityof terminals 210 disposed along the proximal end(s) of the elongateddevice(s) 200 to electrically couple the control module 102 to theelectrodes (134 of FIG. 1) disposed at a distal end of the lead 103.Examples of connectors in control modules are found in, for example,U.S. Pat. Nos. 7,244,150 and 8,224,450, which are incorporated byreference.

FIG. 2B is a schematic side view of another embodiment of the electricalstimulation system 100. The electrical stimulation system 100 includes alead extension 224 that is configured and arranged to couple one or moreelongated devices 200 (e.g., the lead body 106, a splitter, an adaptor,another lead extension, or the like or combinations thereof) to thecontrol module 102. In FIG. 2B, the lead extension 224 is shown coupledto a single port 204 defined in the control module connector 144.Additionally, the lead extension 224 is shown configured and arranged tocouple to a single elongated device 200. In alternate embodiments, thelead extension 224 is configured and arranged to couple to multipleports 204 defined in the control module connector 144, or to receivemultiple elongated devices 200, or both.

A lead extension connector 222 is disposed on the lead extension 224. InFIG. 213, the lead extension connector 222 is shown disposed at a distalend 226 of the lead extension 224. The lead extension connector 222includes a connector housing 228. The connector housing 228 defines atleast one port 230 into which terminals 210 of the elongated device 200can be inserted, as shown by directional arrow 238. The connectorhousing 228 also includes a plurality of connector contacts, such asconnector contact 240. When the elongated device 200 is inserted intothe port 230, the connector contacts 240 disposed in the connectorhousing 228 can be aligned with the terminals 210 of the elongateddevice 200 to electrically couple the lead extension 224 to theelectrodes (134 of FIG. 1) disposed along the lead (103 in FIG. 1).

In at least some embodiments, the proximal end of the lead extension 224is similarly configured and arranged as a proximal end of the lead 103(or other elongated device 200). The lead extension 224 may include aplurality of electrically conductive wires (not shown) that electricallycouple the connector contacts 240 to a proximal end 248 of the leadextension 224 that is opposite to the distal end 226. In at least someembodiments, the conductive wires disposed in the lead extension 224 canbe electrically coupled to a plurality of terminals (not shown) disposedalong the proximal end 248 of the lead extension 224. In at least someembodiments, the proximal end 248 of the lead extension 224 isconfigured and arranged for insertion into a connector disposed inanother lead extension (or another intermediate device). In otherembodiments (and as shown in FIG. 2B), the proximal end 248 of the leadextension 224 is configured and arranged for insertion into the controlmodule connector 144.

Turning to FIG. 3, some conventional percutaneous implantationtechniques involve inserting a lead introducer, such as an epiduralneedle, into a patient. Once the lead introducer is inserted into thepatient, a lead is inserted into the lead introducer and the leadintroducer is positioned at a target stimulation location. Once the leadintroducer is positioned at the target stimulation location, the leadintroducer is removed from the patient, leaving the lead in place.Typically, the lead introducer is removed from the patient by slidingthe lead introducer off the proximal end of the lead.

Unfortunately, when a lead has a body that is not isodiametric, it maybe difficult to slide the lead introducer off the proximal end of thelead. For example, when a proximal end of a lead body has a diameterthat is larger than a distal end of the lead body, or when an oversizedjunction or adapter is disposed along the length of the lead body, thevarying diameters along the length of the lead body may hinder, or evenprevent, the lead introducer from sliding off the proximal end of thelead.

A lateral-release lead introducer (“lead introducer”) uses a multi-pieceinsertion needle that enables a lead to be laterally separated from themulti-piece insertion needle. An example of a lateral-release leadintroducer is found in, for example, U.S. Patent Application PublicationNo. 2011/0224680, which is incorporated by reference.

The lead introducer enables the lead to laterally separate from themulti-piece insertion needle without sliding the multi-piece insertionneedle off the proximal end of the lead. In at least some embodiments,the lead laterally separates from the multi-piece insertion needle bypassing the lead through an open channel defined along a length of themulti-piece insertion needle. In at least some embodiments, duringimplantation of the lead the multi-piece insertion needle is disposed ina splittable member that separates from the lead by splitting apartalong a length of the splittable member.

The multi-piece insertion needle includes an inner needle that isinsertable into an outer needle and that, once inserted into the patientand advanced in proximity to a target stimulation location (e.g., theepidural space of a patient), can be removed from the outer needle. Inat least some embodiments, the distal tip of the outer needle is used topierce patient tissue during insertion and advancement of the leadintroducer into the patient.

As herein described, the multi-piece insertion needle includes a safetyarrangement for reducing the potential for undesirably piercing patienttissue during a lead-implantation procedure. In at least someembodiments, the safety arrangement includes a biasing element thattransitions between a relaxed position and a compressed position. Thetransitioning of the biasing element enables a correspondingtransitioning of the distal tip of the inner needle (which has a blunttip) between a distally-biased position and a retracted position. Whenthe distal tip of the inner needle is in a retracted position, thedistal tip of the inner needle does not extend distally beyond thedistal tip of the outer needle (which has a sharpened tip), and thedistal tip of the outer needle can be used to pierce patient tissue.When the distal tip of the inner needle is in a distally-biasedposition, the distal tip of the inner needle extends distally beyond thedistal tip of the outer needle, and the distal tip of the outer needleis prevented from piercing patient tissue.

In at least some embodiments, the advancement of the lead introducerinto a patient causes a force to be applied against the distal tip ofthe inner needle above a threshold amount. The applied force causes thedistal tip of the inner needle to retract, thereby enabling thesharpened distal tip of the outer insertion needle to pierce patienttissue and advance the lead introducer through the patient tissue. Whenthe force applied against the distal tip of the inner needle is removed,such as when the distal end portion of the lead introducer encounters anopen space within the patient (e.g., when the distal end portion of thelead introducer enters the patient's epidural space), the distal tip ofthe inner needle transitions to the distally-biased position, where theblunt distal tip of the inner needle extends distally from the sharpeneddistal tip of the outer needle, thereby reducing the potential forundesirably piercing patient tissue on or around the open space withoutfurther application of force against the distal tip of the inner needleabove the threshold amount.

FIG. 3 is a schematic perspective exploded view of one embodiment of alead introducer 302 configured and arranged to facilitate implantationof an electrical stimulation system into a patient. The lead introducer302 includes a multi-piece insertion needle 308 and a splittable member350. The multi-piece insertion needle 308 includes an inner needle 310that is insertable into an outer needle 330.

The inner needle 310 has a body 312 with a proximal end portion 314, adistal end portion 316, and a longitudinal length 318. The inner needle310 includes a proximal hub 320 disposed along the proximal end portion314 of the body 312 and a distal tip 322 disposed along the distal endportion 316 of the body 312. The inner needle 310 defines a lumen (526in FIGS. 5A-5B) extending along the longitudinal length 318 of the innerneedle 310. The lumen is described in more detail below, with referenceto FIGS. 5A-5B and 7A-7B.

The outer needle 330 has a body 332 with a proximal end portion 334, adistal end portion 336, and a longitudinal length 338. The outer needle330 includes a proximal hub 340 disposed along the proximal end portion334 of the body 332 and a distal tip 342 disposed along the distal endportion 336 of the body 332. The outer needle 330 defines an openchannel (504 in FIG. 5) extending along the longitudinal length 338 ofthe outer needle 330 and the proximal hub 340. The open channel isdiscussed in more detail below, with reference to FIGS. 5 and 8.

The splittable member 350 has a proximal end portion 354, a distal endportion 356, and a longitudinal length 358. A proximal hub 360 isdisposed along the proximal end portion 354. A lumen (not shown) extendsalong the longitudinal length 356 of the splittable member 350 from theproximal hub 360.

Turning to FIGS. 4A-4B, in at least some embodiments the inner needle310, the outer needle 330, and the splittable member 350 are coupleableto one another such that the inner needle 310, the outer needle 330, andthe splittable member 350 form a nested arrangement.

FIGS. 4A-4B illustrate, in perspective view, one embodiment of the innerneedle 310 disposed in the outer needle 330 which, in turn is disposedin the splittable member 350. As discussed in more detail below, withreference to FIG. 8, the inner needle 310 is disposed in an open channelof the outer needle. In at least some embodiments, the inner needle 310separates from the outer needle 330 when not retained in the openchannel of the outer needle 330 by the splittable member 350.

In FIGS. 4A-4B, the inner needle 310, the outer needle 330, and thesplittable member 350 are shown nested such that the proximal hubs 320,340, and 360 of the inner needle 310, the outer needle 330, and thesplittable member 350, respectively, align axially to one another. InFIGS. 4A-4B, an optional Luer lock collar 402 is shown disposed over theproximal hub 340 of the outer needle 330 and portions of each of theproximal hub 320 of the inner needle 310 and the proximal hub 360 of thesplittable member 350. The Luer lock collar 402 is used for lockingtogether two or more of the proximal hubs 320, 340, and 360 to preventone or more of the inner needle 310, the outer needle 330, or thesplittable member 350 from undesirably rotating relative to one another.

FIG. 4A shows the distal tip 322 of the inner needle 310 disposed in adistally-biased position, where the distal tip 322 of the inner needle310 extends distally relative to the distal tip 342 of the outer needle330 (see e.g., FIG. 5A for a close-up view of the distal tip of theinner needle). The inner needle 310 is disposed in the distally-biasedposition when there is either no force being applied against the distaltip 322 of the inner needle 310 in a proximal direction, or a forcebeing applied against the distal tip 322 of the inner needle 310 isbelow a threshold amount.

FIG. 4B shows the distal tip 322 of the inner needle 310 disposed in aretracted position, where the distal tip 322 of the inner needle 310does not extend distally relative to the distal tip 342 of the outerneedle 330. The inner needle 310 is disposed in the retracted positionwhen there is a force being applied against the distal tip 322 of theinner needle 310 in a proximal direction that is above a thresholdamount.

FIG. 5A illustrates, in perspective view, one embodiment of a distal endportion 502 of the lead introducer 302. FIG. 5B illustrates, inlongitudinal cross-sectional view, one embodiment of the distal endportion 502 of the lead introducer 302. In FIGS. 5A-5B, the inner needle310 is shown disposed in an open channel 504 of the outer needle 330,and the splittable member 350 is shown disposed over portions of theinner needle 310 and the outer needle 330.

In at least some embodiments, the inner needle 310, the outer needle330, and the splittable member 350 are coupleable to one another suchthat the distal end portions 316 and 336 of the inner needle 310 and theouter needle 330, respectively, extend distally beyond the distal endportion 356 of the splittable member 350. In FIGS. 5A-5B, the innerneedle 310 is shown disposed in a distally-biased position, such thatthe distal tip 322 of the inner needle 310 extends distally relative tothe distal tip 342 of the outer needle 330.

In at least some embodiments, the distal tip 342 of the outer needle 330is slanted and is sharpened for piercing patient tissue during insertionof the lead introducer 302 into the patient. In at least someembodiments, the distal tip 322 of the inner needle 310 is blunt toprevent the sharpened distal tip 342 of the outer needle 330 frompiercing patient tissue when the inner needle 310 is disposed indistally-biased position.

The inner needle 310 is formed from any suitable material including, forexample, a flexible plastic resin (e.g., nylon, polyester, polyurethane,or the like), or the like. The inner needle 310 can be formed in anysuitable manner including, for example, extruding. The body 312 of theinner needle 310 can be attached to the proximal hub 320 in any suitablemanner including, for example, adhesive bonding, crimping, or insertionmolding to a plastic or metal inner needle hub.

The inner needle 310 can have any transverse cross-sectional shapesuitable for extending along the open channel 504 of the outer needle330. In at least some embodiments, the inner needle 310 has a transversecross-sectional shape that is oval, oblong, round, or the like.

In at least some embodiments, the body 312 of the inner needle 310 isshaped and sized to slide freely within the open channel 504 of theouter needle 330 with the inner needle 310 only when in a particularcircumferential orientation relative to the outer needle 330. In atleast some embodiments, a key rib 512 is disposed along the body 312 ofthe inner needle 310. In at least some embodiments, the key rib 512extends along the entire longitudinal length 318 of the body 312 of theinner needle 310. Alternately, the key rib 512 extends along less thanthe entire longitudinal length 318 of the body 312 of the inner needle310. An example of a lead introducer with an inner needle having a keyrib is found in, for example, U.S. patent application Ser. No. ______,(Attorney Docket No. 1362009-2337) filed on even date herewith, entitled“Systems and methods for making and using a lead introducer for animplantable electrical stimulation system”, which is incorporated byreference.

The key rib 512 engages the open channel 504 of the outer needle 330 tofacilitate sliding of the inner needle 310 relative to the open channel504. The key rib 512 extends along a particular circumferential portionof the inner needle 310 such that, in at least some embodiments, whenthe inner needle 310 is extended along the open channel 504, the key rib512 is disposed directly between opposing edges of the open channel 504(i.e., the key rib 512 is circumferentially opposed to a trough portionof a transverse cross-section of the open channel 504).

In at least some embodiments, a lumen 526 is defined along a portion ofthe longitudinal length 318 of the inner needle 310. The lumen 526 ofthe inner needle 310 is suitable for using to check for precisepositioning of the lead introducer 302 during, for example, aloss-of-resistance test. In at least some embodiments, the proximal hub320 of the inner needle 310 is suitable for receiving a syringe andintroducing fluid into the lumen 526. In at least some embodiments,fluid (e.g., saline solution, air, or the like) may be introduced to, orremoved from, the patient, via the lumen 526, to check for precisepositioning of the lead introducer 302, for example, whether or not theepidural space has been entered.

In at least some embodiments, the lumen 526 opens along the distal endportion 316 of the inner-needle body 312 at a location that is proximalto the inner-needle distal tip 310. It may be advantageous for the lumen526 to not open along the distal tip 322 to avoid undesired coring ofpatient tissue during advancement of the lead introducer into thepatient.

Turning to FIG. 6, the transitioning of the distal tip of the innerneedle between the distally-biased position and the retracted positionis enabled by a biasing element. FIG. 6 illustrates proximal endportions of the inner needle 310, the outer needle 330, and thesplittable sheath 350 nested together. The proximal hubs of the innerneedle 310, the outer needle, 330 and the splittable sheath 350 are heldtogether by the Luer lock collar 402. In FIG. 6, outer surfaces of theinner needle, the outer needle, and the splittable sheath are shown asbeing transparent, for clarity of illustration.

An optional Luer fitting 612 is disposed along the proximal hub 320 ofthe inner needle 310. The Luer fitting 612 is in fluid communicationwith the lumen 526 of the inner-needle body 312 and can be used during,for example, a loss-of-resistance test. In at least some embodiments,the Luer fitting 612 is suitable for receiving a syringe. In at leastsome embodiments, fluid (e.g. saline solution, air, or the like) may beintroduced to, or removed from, the patient, via the Luer fitting 612and the lumen 526, to check for precise positioning of the leadintroducer 302, for example, whether or not the epidural space has beenentered.

A safety arrangement 602 is disposed along the proximal end portions ofthe inner needle 310 and the outer needle 330. The safety arrangement607 includes a biasing element 604. In FIG. 6 and in other figures, thebiasing element 604 is shown as a coiled spring. It will be understoodthat biasing elements can take forms other than a coiled spring.

The distal tip 322 of the inner needle 310 transitions between thedistally-biased position and the retracted position using the biasingelement 604. The biasing element 604 can be disposed along any suitableportion of the inner needle 330. In at least some embodiments, thebiasing element 604 is disposed in the proximal hub 320 of the innerneedle 310.

In embodiments utilizing a coiled spring as the biasing element 604, thethreshold amount of force needed to transition the distal tip 322 of theinner needle 310 between the distally-biased position and the retractedposition is determined, at least in part, by a k-value of the spring.Hooke's Law states that F=kx, where k is a constant factorcharacteristic of a spring. Thus, according to Hooke's Law, the amountof Force, F, needed to cause the spring to travel a distance, x, isdetermined based on the k-value of the spring. Therefore, in at leastsome embodiments the threshold amount of force needed to transition thedistal tip 322 of the inner needle 310 between the distally-biasedposition and the retracted position is determined, as least in part, bythe k-value of the spring.

The transition threshold needed to exceed for transitioning the distaltip 322 of the inner needle 310 from the distally-biased position to theretracted position can be any suitable amount of force. In at least someembodiments, the transition threshold is set at a level of force that isless than an amount of force typically applied against the distal tip ofthe inner needle during insertion of the lead introducer into thepatient. For example, the transition threshold may be set to a level offorce that is less than an amount of force typically applied against thedistal tip of the inner needle during insertion of the lead introducerinto the into a patient's back and the subsequent advancement of thelead introducer into the patient's epidural space. In at least someembodiments, the transition threshold is set at a level of force that isno less than 50%, 60%, 70%, 80%, 90% of the amount of force typicallyapplied against the distal tip of the inner needle during insertion ofthe lead introducer into the patient.

In the present case, the distance over which the biasing element 604 iscompressed from a relaxed position can be proportional to the distancemoved by the distal tip 322 of the inner needle 310 as the distal tip322 of the inner needle 310 moves relative to the distal tip 342 of theouter needle 330 when transitioning between the distally-biased positionand the retracted position. In at least some embodiments, the distal tip322 of the inner needle 310 is rigidly coupled to the biasing element604. Thus, in at least some embodiments the distance over which thebiasing element 604 is compressed from a relaxed position to thecompressed position is equal to the distance moved by the distal tip 322of the inner needle 310 as the distal tip 322 of the inner needle 310moves relative to the distal tip 342 of the outer needle 330 whentransitioning from the distally-biased position to the retractedposition.

FIGS. 7A-7C illustrate, in longitudinal cross-section, one embodiment ofthe proximal end portions of the inner needle 310, the outer needle 330,and the splittable sheath 350 nested together. The proximal hubs of theinner needle 310, the outer needle, 330 and the splittable sheath 350are held together by the Luer lock collar 402.

In FIGS. 7A-7C, the proximal hub 320 of the inner needle 310 is shownhaving a first portion 702 and a second portion 712. The first portion702 includes a cavity 704 suitable for housing the biasing element 604and a proximal portion of the second portion 712 of the proximal hub320. In at least some embodiments, the outer-needle proximal hub 340defines a recess 720 that is disposed along a proximal end of theinner-needle proximal hub 320 and that is suitable for receiving adistal portion of the second portion 712 of the inner-needle proximalhub 320.

In FIGS. 7A-7C, the Luer fitting 612 is shown disposed in the firstportion 702 of the inner-needle proximal hub 320. The Luer fitting 612is in fluid communication with the lumen 526 of the inner-needle body312 via a tube 706 disposed in the cavity 704 of the first portion 702of the inner-needle proximal hub 320. In at least some embodiments, thetube 706 extends through coils of the biasing element 604. In at leastsome embodiments, the tube 706 is in fluid communication with the lumen526 of the inner-needle body 312 via a lumen 714 defined in the secondportion 712 of the inner-needle proximal hub 320.

In at least some embodiments, a watertight seal 730 is disposed betweenthe first portion 702 and the second portion 712 of the inner-needleproximal hub 320 for preventing undesired liquids from entering thecavity 704 in proximity to the biasing element 604. In at least someembodiments, the watertight seal 730 is Formed as on O-ring. In at leastsome embodiments, the watertight seal 730 is disposed along an annulargroove 734 defined along an outer surface of the second portion 712 ofthe inner-needle proximal hub 320.

In at least some embodiments, a lock pin 740 is coupled to theinner-needle proximal hub 320. The lock pin 740 can be used to limit themovement of the biasing element 604 when the biasing element 604 istransitioned between a relaxed position and a compressed position, andvice versa. The lock pin 740 may also be used to maintaincircumferential alignment between the first portion 702 and the secondportion 712 of the inner-needle proximal hub 320. In at least someembodiments, the lock pin 740 is attached (e.g., press-fit, bonded,welded, or the like) to an aperture formed along the first portion 702of the inner-needle proximal hub 320. In at least some embodiments, thelock pin 740 engages with a slot that extends along a length of thesecond portion 712 of the inner-needle proximal hub 320 (i.e., in thedirection that is parallel to the direction of travel of the biasingelement 604).

FIGS. 7A-7C show the positioning of the biasing element during anexemplary lead-implantation procedure into an epidural space of apatient. As described above, the biasing element 604 controls axialmovement of the inner-needle body. The blunt distal tip of the innerneedle extends distally from the sharpened distal tip of the outerneedle in the absence of a force (or the presence of force that is weakenough to be below the k-value of the biasing element) being applied ina proximal direction against the blunt distal tip of the inner needle.The distally-extending inner-needle distal tip obstructs the sharpenedouter-needle distal tip.

When a sufficiently-strong force is applied in a proximal directionagainst the blunt distal tip of the inner needle, the biasing elementcompresses and the blunt distal tip of the inner needle retracts,thereby exposing the sharpened distal tip of the outer needle (i.e., theinner needle does not extend distally more than a small amount, if atall, from the distal tip of the outer needle). In other words, thedistal tip of the inner needle is distally-biased when the biasingelement is in a relaxed position; and the distal tip of the inner needleretracts when the biasing element compresses.

In FIG. 7A, the biasing element 604 is shown disposed in a relaxedposition. Accordingly, the distal tip 322 of the inner needle 310 isdisposed in the distally-biased position and the sharpened distal tip ofthe outer needle is obstructed from contacting patient tissue. In atleast some embodiments, the inner needle 310 is disposed in thedistally-biased position prior to insertion of the lead introducer intothe patient.

In FIG. 7B, the biasing element 604 is shown disposed in a compressedposition. Accordingly, the distal tip 322 of the inner needle 310 isdisposed in the retracted position and the sharpened distal tip of theouter needle is exposed. In at least some embodiments, the inner needle310 is disposed in the retracted position during insertion of the leadintroducer into the patient, and advancement of the lead introducer tothe patient's epidural space.

In FIG. 7C, the biasing element 604 is shown disposed in a relaxedposition. Accordingly, the distal tip 322 of the inner needle 310 isdisposed in the distally-biased position. In at least some embodiments,the inner needle 310 transitions to the distally-biased position whenthe distal tip 322 of the inner needle 310 enters the patient's epiduralspace. In at least some embodiments, the distal tip 322 of the innerneedle 310 maintains the distally-biased position while disposed in theepidural space.

Turning to FIG. 8, the outer needle is designed to sequentially receivethe inner needle and a lead during a lead-implantation procedure, suchthat the inner needle and the lead are not simultaneously received bythe outer needle. The inner needle and the lead are received by the openchannel extending along the longitudinal length of the outer needle.

FIG. 8 illustrates, in perspective view, one embodiment of a distal endportion of a lead 802 and a portion of the outer needle 330. The openchannel 504 is defined along the longitudinal length 338 of the outerneedle 310. As shown in FIG. 8, the open channel 504 may also extendalong the proximal hub 340 of the outer needle 330.

In some embodiments, the lead 802 has an isodiametric lead body. Inother embodiments, the lead 802 has a non-isodiametric lead body. In atleast some embodiments, the lead 802 includes one or more elements(e.g., a junction, adaptor, or the like) disposed along the length ofthe lead 802 which has a transverse cross-sectional shape or size thatis different from the distal end portion of the lead 802. In at leastsome embodiments, the distal end portion of the lead 802 has atransverse cross-sectional shape that is similar to a cross-sectionalshape of the inner needle 310. In at least some embodiments, the one ormore elements of the lead 802 having a different transversecross-sectional shape or size from the distal end portion of the lead802 are disposed along a proximal end portion of the lead 802.

In at least some embodiments, the inner needle 310 is shaped such thatthe inner needle 310 does not separate laterally from the open channel504 when the inner needle 310 is received by the outer needle 330. Inalternate embodiments, the inner needle 310 is free to separatelaterally from the open channel 504 of the outer needle 330 when theinner needle 310 is received by the outer needle 330. In at least someembodiments, the inner needle 310 is insertable into, and removablefrom, the open channel 504 of the outer needle 330 solely by sliding theinner needle 310 axially along the open channel 504. In at least someembodiments, the inner needle 310 is configured and arranged to at leastsubstantially fill the open channel 504 when the inner needle 310 isdisposed in the open channel 504.

The open channel 504 is configured and arranged to receive the lead 807when the inner needle 310 is not disposed in the open channel 504. In atleast some embodiments, the lead 802 is free to separate laterally fromthe open channel 504 of the outer needle 330 when the inner needle 310is received by the outer needle 330. In at least some embodiments, thelead 802 is insertable into, and removable from, the open channel 504 ofthe outer needle 330 by sliding the lead 802 axially along the openchannel 504.

In at least some embodiments, the open channel 504 is configured andarranged to receive the lead 802 such that the lead 802 is separatablefrom the open channel 504 without moving the lead 802 axially relativeto the outer needle 330. In at least some embodiments, the open channel504 has a width that is no less than a diameter of the lead 802.

In at least some embodiments, the lead 802 has a diameter that is largerthan the space between the two opposing edges of the open channel 504 ofthe outer needle 330. In which case, the lead 802 typically does notpass laterally through the open channel 504 due solely to the force ofgravity. The body of the lead 802 is typically formed from a deformablematerial. In at least some embodiments, the lead 802 is removable fromthe open channel 504 by applying enough lateral force to at least one ofthe lead 802 or the outer needle 330 to deform the lead enough to enablethe lead 802 to be passed laterally out through the open channel 504.

The open channel 504 can have any transverse cross-sectional shapesuitable for sequentially retaining the inner needle 310 and the lead802. In at least some embodiments, the open channel 504 has a transversecross-sectional shape that is U-shaped 710. Alternately, the openchannel 504 can have a transverse cross-section that ishorseshoe-shaped, C-shaped, or the like.

Turning to FIG. 9, one embodiment of a lead-implantation procedure isdescribed using the lead introducer 302 to implant the lead 802 at atarget stimulation location. The inner needle 310 is inserted into theopen channel 504 of the outer needle 330, and the outer needle 330 isinserted into the splittable member 350, as shown in FIGS. 4A-4B. Itwill be understood that, in some embodiments, the lead introducer 302 ispre-assembled during manufacture.

The assembled lead introducer 302 is inserted into a patient and guidedin proximity to the target stimulation location (e.g., several vertebraelevels above or below the target stimulation location). In at least someembodiments, once the lead introducer 302 is in proximity to a targetstimulation location fluid is introduced or removed through inner needle310 to check for precise positioning of the lead introducer 302, forexample, in an epidural space of the patient.

FIG. 9 is a schematic perspective view of one embodiment of the innerneedle 310 inserted into the open channel 504 of the outer needle 330which, in turn, is inserted into the splittable member 350. In FIG. 9,the inner needle 310, the outer needle 330, and the splittable member350 are partially disposed in a patient, as shown by a dotted line 902.The distal end portions of the inner needle 310, the outer needle 330,and the splittable member 350 are advanced to a location in proximity tothe target stimulation location.

Turning to FIG. 10, once the lead introducer 302 is positioned in theepidural space in proximity to the target stimulation location, theinner needle 310 may be removed and the distal end portion of the lead802 may be inserted into the open channel 504 of the outer needle 330and the proximal opening of the sheath 350. FIG. 10 is a schematicperspective view of one embodiment of the distal end portion of the lead802 inserted into the open channel 504 of the outer needle 330 via theproximal hub 320. Once the distal end portion of the lead 802 isinserted into the open channel 504 of the outer needle 330, the distalend portion of the lead 802 may be guided more closely to the targetstimulation region. In at least some embodiments, the distal end portionof the lead 802 is guided to the target stimulation region by thecomparably-rigid outer needle 330.

It may be advantageous to guide the lead 802 within the patient whilethe lead 802 is disposed in the outer needle 330 and the splittablemember 350. The outer needle 330 and the splittable member 350 mayprovide the medical practitioner with the ability to steer the leadintroducer 302 by applying a lateral force of the lead introducer 302 todirect the trajectory of the lead 802. When the outer needle 330 isremoved from the lead 802 prior to insertion, then the splittable member350 may be too flexible to provide this steering ability.

Once the distal end portion of the lead 802 has been guided to thetarget stimulation location, the splittable member 350 and the outerneedle 330 may be separated from the lead 802 and removed from thepatient. It will be understood that the splittable member 350 may beseparated from the lead 802 either before or after the outer needle 330is separated from the lead 802. It will also be understood that thesplittable member 350 may be removed from the patient either before orafter the outer needle 330 is removed from the patient. In someembodiments, the outer needle 330 is separated from the lead 802 priorto the splittable member 350 being separated from the lead 802. In otherembodiments, the splittable member 350 is separated from the lead 802prior to the outer needle 330 being separated from the lead 802. In someembodiments, the outer needle 330 is removed from the patient prior toremoval of the splittable member 350. In other embodiments, thesplittable member 350 is removed from the patient prior to removal ofthe outer needle 330.

In at least some embodiments, the lead 802 is guided to the targetstimulation location while disposed in the outer needle 330 and thesplittable member 350. The outer needle 330 is removed from the lead 802(and from the patient). The splittable member 350 is then split apartfrom the lead 802 and removed from the patient.

FIG. 11 is a schematic perspective view of one embodiment of thesplittable member 350 being split apart to remove the splittable member350 from the lead 802. The proximal hub 360 of the splittable member 350includes at least two pull-apart tabs 1102 and 1104 suitable forfacilitating splitting of the splittable member 350.

In at least some embodiments, the splittable member 350 is formed from aflexible material suitable for implantation into the patient 902including, for example, fluorinated ethylene propylene,polytetrafluoroethylene, high-density polyethylene,polyetheretherketone, and the like or combinations thereof.Additionally, one or more radiopaque materials may be added including,for example, barium sulfate and bismuth subcarbonate, and the like orcombinations thereof to facilitate implantation of the introducer sheaththrough the use of one or more medical imaging techniques, such asfluoroscopy.

In at least some embodiments, the splittable member includes one or moreperforated (or scored, or the like) regions 1106 extending along atleast a portion of the longitudinal length 358 of the splittable member350 from between the at least two pull-apart tabs 1102 and 1104. In atleast some embodiments, when the at least two pull-apart tabs 1102 and1104 are separated from one another, for example, by pulling eachpull-apart tab laterally (i.e., away from the other pull-apart tab(s) indirections approximately orthogonal to the splittable member 350), thesplittable member 350 separates along the one or more perforated regions1106.

In at least some embodiments, the splittable member 350 is separatedinto multiple longitudinal strips while pulling the splittable member350 proximally along the lead 802. As the splittable member 350 splitsapart, the distal end portion 356 of the splittable member 350 (notshown in FIG. 11) moves proximally along the lead 802 (as shown by arrow1108), with an increasing amount of the lead 802 extending through thedistal end portion 356 of the splittable member 350. In at least someembodiments, an undersurface of the splittable member 350 includes alubricious coating to facilitate the proximal movement of the splittablemember 350.

Eventually, the splittable member 350 may be completely separated intotwo or more longitudinal strips, thereby separating completely from thelead 802 and also from the patient. In at least some embodiments, thedistal end portions of the splittable member 350 are extracted from thepatient as the splittable member 350 is split apart. In at least someembodiments, the splittable member 350 is split apart without causingthe lead 802 to move.

Once the lead 802 is positioned at the target stimulation location, thelead 802 may be coupled to a control module (e.g., 102 of FIG. 1) andimplanted using well-known techniques, for example, using one or moretunneling straws placed in passageways underneath patient skin withbores that are sized large enough to receive the lead 802. In at leastsome embodiments, the lead 802 is coupled directly to a connector of acontrol module, as shown in FIG. 3. In other embodiments, the lead 802is coupled to the control module via one or more other devices,including an adaptor, a lead extension, an operating room cable, or thelike or combinations thereof.

FIG. 12 is a schematic overview of one embodiment of components of anelectrical stimulation system 1200 including an electronic subassembly1210 disposed within a control module. It will be understood that theelectrical stimulation system can include more, fewer, or differentcomponents and can have a variety of different configurations includingthose configurations disclosed in the stimulator references citedherein.

Some of the components (for example, a power source 1212, an antenna1218, a receiver 1202, and a processor 1204) of the electricalstimulation system can be positioned on one or more circuit boards orsimilar carriers within a sealed housing of an implantable pulsegenerator, if desired. Any power source 1212 can be used including, forexample, a battery such as a primary battery or a rechargeable battery.Examples of other power sources include super capacitors, nuclear oratomic batteries, mechanical resonators, infrared collectors,thermally-powered energy sources, flexural powered energy sources,bioenergy power sources, fuel cells, bioelectric cells, osmotic pressurepumps, and the like including the power sources described in U.S. Pat.No. 7,437,193 incorporated herein by reference.

As another alternative, power can be supplied by an external powersource through inductive coupling via the optional antenna 1218 or asecondary antenna. The external power source can be in a device that ismounted on the skin of the user or in a unit that is provided near theuser on a permanent or periodic basis.

If the power source 1212 is a rechargeable battery, the battery may berecharged using the optional antenna 1218, if desired. Power can beprovided to the battery for recharging by inductively coupling thebattery through the antenna to a recharging unit 1216 external to theuser. Examples of such arrangements can be found in the referencesidentified above.

In one embodiment, electrical current is emitted by the electrodes 134on the paddle or lead body to stimulate nerve fibers, muscle fibers, orother body tissues near the electrical stimulation system. The processor1204 is generally included to control the timing and electricalcharacteristics of the electrical stimulation system. For example, theprocessor 1204 can, if desired, control one or more of the timing,frequency, strength, duration, and waveform of the pulses. In addition,the processor 1204 can select which electrodes can be used to providestimulation, if desired. In some embodiments, the processor 1204 selectswhich electrode(s) are cathodes and which electrode(s) are anodes. Insome embodiments, the processor 1204 is used to identify whichelectrodes provide the most useful stimulation of the desired tissue.

Any processor can be used and can be as simple as an electronic devicethat, for example, produces pulses at a regular interval or theprocessor can be capable of receiving and interpreting instructions froman external programming unit 1208 that, for example, allows modificationof pulse characteristics. In the illustrated embodiment, the processor1204 is coupled to a receiver 1202 which, in turn, is coupled to theoptional antenna 1218. This allows the processor 1204 to receiveinstructions from an external source to, for example, direct the pulsecharacteristics and the selection of electrodes, if desired.

In one embodiment, the antenna 1218 is capable of receiving signals(e.g., RF signals) from an external telemetry unit 1206 which isprogrammed by the programming unit 1208. The programming unit 1208 canbe external to, or part of, the telemetry unit 1206. The telemetry unit1206 can be a device that is worn on the skin of the user or can becarried by the user and can have a form similar to a pager, cellularphone, or remote control, if desired. As another alternative, thetelemetry unit 1206 may not be worn or carried by the user but may onlybe available at a home station or at a clinician's office. Theprogramming unit 1208 can be any unit that can provide information tothe telemetry unit 1206 for transmission to the electrical stimulationsystem 1200. The programming unit 1208 can be part of the telemetry unit1206 or can provide signals or information to the telemetry unit 1206via a wireless or wired connection. One example of a suitableprogramming unit is a computer operated by the user or clinician to sendsignals to the telemetry unit 1206.

The signals sent to the processor 1204 via the antenna 1218 and thereceiver 1202 can be used to modify or otherwise direct the operation ofthe electrical stimulation system. For example, the signals may be usedto modify the pulses of the electrical stimulation system such asmodifying one or more of pulse duration, pulse frequency, pulsewaveform, and pulse strength. The signals may also direct the electricalstimulation system 1200 to cease operation, to start operation, to startcharging the battery, or to stop charging the battery. In otherembodiments, the stimulation system does not include the antenna 1218 orreceiver 1202 and the processor 1204 operates as programmed.

Optionally, the electrical stimulation system 1200 may include atransmitter (not shown) coupled to the processor 1204 and the antenna1218 for transmitting signals back to the telemetry unit 1206 or anotherunit capable of receiving the signals. For example, the electricalstimulation system 1200 may transmit signals indicating whether theelectrical stimulation system 1200 is operating properly or not orindicating when the battery needs to be charged or the level of chargeremaining in the battery. The processor 1204 may also be capable oftransmitting information about the pulse characteristics so that a useror clinician can determine or verify the characteristics.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A lead introducer comprising: an outer needlecomprising an outer-needle body having a proximal end portion, a distalend portion, and a longitudinal length, a sharpened distal tip disposedalong the distal end portion of the outer-needle body, and an openchannel extending along the entire longitudinal length of theouter-needle body; an inner needle configured and arranged for slidingalong the open channel of the outer needle, the inner needle comprisingan inner-needle body having a proximal end portion, a distal endportion, and a longitudinal length, a blunt distal tip disposed alongthe distal end portion of the inner-needle body, and an inner-needleproximal hub attached to the proximal end portion of the inner-needlebody: a biasing element coupled to the inner-needle body, the biasingelement configured and arranged to facilitate a transition of the distaltip of the inner needle between a distally-biased position, where thedistal tip of the inner needle obstructs the sharpened distal tip of theouter needle, and a retracted position, where the distal tip of theinner at least partially exposes the distal tip of the outer needle; anda splittable member having at least one perforated region extendingalong a longitudinal length of the splittable member, the splittablemember configured and arranged for disposing over the outer-needle bodyand the inner-needle body when the inner-needle body is disposed in theopen channel of the outer-needle body and for separating from theouter-needle body and the inner-needle body by separating along the atleast one perforated region.
 2. The lead introducer of claim 1, whereinthe biasing element is disposed in the inner-needle proximal hub.
 3. Thelead introducer of claim 1, wherein the inner-needle proximal hubcomprises: a first portion defining a cavity for receiving the biasingelement; and a second portion partially disposed in the cavity of thefirst portion of the inner-needle proximal hub.
 4. The lead introducerof claim 3, wherein the outer needle comprises an outer-needle proximalhub attached to the proximal end portion of the outer-needle body, theouter-needle proximal hub defining a recess along a distal end of theouter-needle proximal hub.
 5. The lead introducer of claim 4, whereinthe second portion of the inner-needle proximal hub is partiallydisposed within the recess while concurrently being partially disposedin the cavity of the first portion of the inner-needle proximal hub whenthe inner-needle body is disposed in the open channel of theouter-needle body.
 6. The lead introducer of claim 3, wherein theinner-needle proximal hub further comprises a watertight seal disposedbetween the first portion and the second portion of the inner-needleproximal hub.
 7. The lead introducer of claim 6, wherein the watertightseal is disposed in an annular groove defined along an outer surface ofthe second portion of the inner-needle hub.
 8. The lead introducer ofclaim 1, wherein the inner-needle proximal hub further comprises a lockpin for limiting travel of the biasing element when the biasing elementis transitioned to a compressed position.
 9. The lead introducer ofclaim 1, wherein the biasing element comprises a coiled spring.
 10. Thelead introducer of claim 1, further comprising a Luer fitting disposedalong the inner-needle proximal hub, the Luer fitting configured andarranged to receive a syringe.
 11. The lead introducer of claim 10,further comprising a tube disposed in the inner-needle proximal hub andextending between the Luer fitting and the lumen of the inner-needlebody.
 12. The lead introducer of claim 1, wherein the inner-needle bodydefines a lumen extending distally from the inner-needle proximal hub.13. The lead introducer of claim 1, wherein the splittable membercomprises: a proximal hub with at least two pull-apart tabs, and a lumenconfigured and arranged for receiving the outer-needle body and theinner-needle body, wherein the at least one perforated region isconfigured and arranged for separating when the at least two pull-aparttabs are pulled apart from one another in directions approximatelyorthogonal to the splittable member.
 14. An insertion kit comprising:the lead introducer of claim 1; a neurostimulation lead configured andarranged for implantation into a patient, the neurostimulation leadcomprising a lead body having a distal end portion and a proximal endportion, a plurality of electrodes disposed at the distal end portion ofthe lead body, a plurality of terminals disposed at the proximal endportion of the lead body, and a plurality of conductive wires couplingthe plurality of electrodes electrically to the plurality of terminals;and wherein the open channel of the outer needle is configured andarranged such that, when the inner needle of the lead introducer is notinserted in the open channel, the distal end portion of the lead body isinsertable into the open channel with the lead body being laterallyseparatable from the outer needle of the lead introducer through theopen channel of the outer needle.
 15. An electrical stimulation systemcomprising: the insertion kit of claim 14; a control module configuredand arranged to electrically couple to the neurostimulation lead of theinsertion kit, the control module comprising a housing, and anelectronic subassembly disposed in the housing; and a connector forreceiving the neurostimulation lead, the connector comprising aconnector housing defining a port for receiving the proximal end portionof the lead body, and a plurality of connector contacts disposed in theconnector housing, the connector contacts configured and arranged tocouple to the plurality of terminals of the neurostimulation lead whenthe proximal end portion of the neurostimulation lead is received by theconnector housing.
 16. A method for implanting a neurostimulation leadinto a patient, the method comprising: advancing a distal end portion ofthe lead introducer of claim 1 into the patient; removing the innerneedle of the lead introducer from the patient, leaving the outer needleand splittable member of the lead introducer within the patient;inserting into the open channel of the outer needle a distal end portionof a neurostimulation lead, the neurostimulation lead comprising aplurality of electrodes disposed along the distal end portion of theneurostimulation lead and a plurality of terminals disposed along aproximal end portion of the neurostimulation lead; separating thesplittable member; removing the splittable member and the outer needlefrom the patient, leaving the neurostimulation lead implanted in thepatient at a target stimulation location in proximity to the open space.17. The method of claim 16, wherein advancing a distal end portion ofthe lead introducer into the patient comprises advancing the distal endportion of the lead introducer from an outer surface of the patient toan open space within the patient.
 18. The method of claim 17, whereinadvancing a distal end portion of the lead introducer from an outersurface of the patient to an open space within the patient comprises:advancing the distal end portion of the lead introducer from the outersurface to the open space with the distal tip of the inner needle of thelead introducer in the retracted position; and transitioning the distaltip of the inner needle of the lead introducer from the retractedposition to the distally-biased position when the distal end portion ofthe lead introducer enters the open space.
 19. The method of claim 17,wherein advancing a distal end portion of the lead introducer from anouter surface of the patient to an open space within the patientcomprises advancing the distal end of the lead introducer from the outersurface of the patient to the patient's epidural space.
 20. The methodof claim 17, wherein advancing a distal end portion of the leadintroducer from an outer surface of the patient to an open space withinthe patient comprises transitioning the distal tip of the inner needleto the retracted position when the outer surface of the patient ispierced by the distal end portion of the lead introducer.